Mobile devices, such as smartphones, tablets and laptops location services enable location based applications or services to be provided on the devices. These services require that the mobile device determine their current location, or an estimate of the location using location technology such as a global positioning system (GPS) receiver. However a GPS receiver or signal may not always be available, or its accuracy too low due to the particular radio frequency environment, and an accurate location for the mobile device may be able to be determined.
It is possible to estimate a location of a mobile device based on a radio scene captured by the mobile device, however an accurate location of the associated transceivers is required to provide location estimate. The radio scene may comprise a plurality of cell identifiers (IDs) and associated received signal strength indicator (RSSI) value from cellular transceivers the mobile device is receiving signals from. If the locations of the transceivers are known, the location of the mobile device can be estimated using trilateration, or more generally n-lateration.
FIG. 1 depicts the use of trilateration for determining a location of a mobile device. In FIG. 1, it is assumed that the person 102 has a mobile device. The mobile device may communicate with numerous cell sites 104a, 104b, 104c having transceivers (referred to collectively as cell sites 104). If the position of the cell sites 104 are known, and a distance 106, 106b, 106c from each of the cell sites 104 to the person 102 is known, it is possible to determine the location of the person using trilateration, which is the case of n-lateration for n=3. The signal strength of signals 108a, 108b, 108c received at the user's mobile device from the cell sites 104 can be used to provide an estimate of the distance the user is from the transceivers of the respective cell sites 104. The mobile device may provide a current radio scene to a location service that can provide the required location information of the cell site. The location service can perform the trilateration and return the estimate of the mobile device's location back to the mobile device, which can then use the estimated location as desired.
FIG. 2 depicts an illustrative representation of determining a location of a cell site. The cell site 202 communicates with a plurality of users 204a,204b, 204c, 204d, 204e, 204f (referred to collectively as users 204), or more precisely the mobile devices of the users 204, that are within a transmission radius 206 of the transceiver of the cell site 202. If the locations of the users 204 are known as well as the distances 208a, 208b, 208c, 208d, 208e, 208f from the users 204 to the cell site 202, the location of the cell site 202 can be determined. Additionally or alternatively, if a large number of users provide their location information, the location of the cell site can be estimated as a centroid of the provided mobile device locations.
While the above technique for determining a cell site's location as a centroid of mobile device positions works well if the users providing their location information are evenly distributed about the transceiver of cell site, the technique will provide a location estimate with a larger error if the users are not evenly located about the transceiver of the cell site, as may be the case for co-located transceivers of sectored cell sites.
As described above, in order to provide a location service when GPS information is not available or is inaccurate from the mobile device, the location of cell sites must be known to use network based location techniques. Although the wireless carriers, or infrastructure service providers, that operate the wireless network will know the location of the cell sites to a high degree of accuracy and can use network based location techniques to determine a location of a mobile device, this information is often not available to third parties or applications that may wish to provide location services to mobile devices. As such, it is necessary to be able to accurately determine the location of cell sites in a network in order to provide location services without relying on service provider location information.
Therefore there is a need for a system and method for improved location estimates of co-located sectored cell sites.